A major objective of layer 2 protocols in wireless access networks is to provide improved radio link quality and reliability by implementing a retransmission mechanism for non-delay-sensitive services and applications. For the Global System for Mobile Communication (GSM) standard, the radio link protocol (RLP) uses automatic repeat request (ARQ) protocol. An Internet Protocol (IP) based RLP design allows an RLP frame to encapsulate an IP packet or fragment of an IP packet. Each RLP frame header includes a sequence number to maintain the integrity of RLP frames flowing over the wireless link. In a negative acknowledgment (NAK) based RLP ARQ scheme, after identifying the loss of an RLP frame at the receiver side RLP entity, a NAK message is sent to the transmitter side RLP entity. The NAK message triggers a retransmission of the RLP frame by the transmitter side RLP entity. Lost RLP frames are determined by checking the sequence numbers of RLP frames. Once an RLP frame is lost, a significant amount of time may pass before receiving a subsequent RLP frame, which is capable of providing information to determine that the previous RLP frame was lost. Such delays reduce overall throughput.
For example, the reception of RLP frames N and N+2 in a row indicates that RLP frame N+1 was lost. After receiving RLP frame N+2, the receiver side RLP entity sends a NAK to request retransmission of frame N+1. In a high-speed wireless Internet access system, arrival times for frames often vary greatly due to the high non-stream-like nature, or burstiness, of packet applications. If frame N+2 arrives at the receiver a relatively long time after N, then the receiver RLP layer will take a longer period of time to identify the possible loss of frame N+1. The result is a longer wireless link delay for frame N+1. Also, for a wireless access system with a shared downlink channel having a large bandwidth, a data transmission scheduler can further increase retransmission delays. For example, the scheduler may schedule frame N+2 a long time after scheduling packet N+1 due to the real-time traffic load, scheduling algorithms, and the like. Accordingly, the loss or corruption of frame N+1 will not be determined until frame N+2 is scheduled for transmission, transmitted and subsequently received.
Current detection and retransmission techniques significantly impair overall throughput to maintain an acceptable level of reliability or Quality of Service (QoS). Accordingly, there is a need to minimize the time required to identify lost or corrupt RLP frame and to decrease the delay in retransmitting the lost or corrupt RLP frames without sacrificing reliability.